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To get a better understanding of the characteristics of the high pressure gasoline sprays impinging on a wall, a fundamental study was conducted in a high-temperature high-pressure constant volume vessel under the simulated engine conditions of in-cylinder pressures, temperatures, and wall temperatures. The injection pressure was varied from 20 to 120 MPa. The spray tip penetration, vapor mass distribution, and vaporization rate were quantitatively measured with the laser absorption-scattering (LAS) technique. The velocity fields of the wall-impinging sprays under vaporizing conditions were measured with the particle image velocimetry (PIV) technique using silicone oil droplets as tracers. The effects of injection pressure and spray/wall interactions on spray characteristics were investigated. The results showed that the increased injection pressure improved penetration, vaporization, and turbulence of the sprays.

Three-Dimensional visualization technique based on volume rendering method has been developed in order to translate a calculated result of diesel combustion simulation into an realistically spray and flame image. This paper presents an overview of diesel combustion model which has been developed at Hiroshima University, a description of the three-dimensional visualization technique, and some examples of spray and flame image generated by this visualization technique.

Different ethanol-gasoline blended fuels, namely the E0 (100% gasoline), E85 (85% ethanol and 15% gasoline mixed in volume basis) and E100 (100% ethanol) were injected by a valve-covered-orifice (VCO) hole-type nozzle in a condition simulating the near top dead center (TDC). Two typical injection pressures of 10 and 20MPa were adopted to clarify the spray and flame behaviors. The correlation of the upstream unburned fuel and the flame propagation was analyzed by the high-speed imaging of shadowgraph. Moreover, the effects of ignition timing and location on the flame propagation were discussed based on the imaging of OH* chemiluminescence.

Reduction of orifice diameter of nozzle is advantageous to the fuel atomization in a D.I. diesel engine. However, the diameter reduction is usually accompanied with decrease of spray tip penetration, thus worsening fuel spatial-distribution and fuel-air mixing. In this paper, a group-hole nozzle concept was proposed to solve the problem resulting from minimization of orifice diameter. Compared to the conventional multi-hole nozzle, group-hole nozzle has a series group of orifices, and each group consists of two micro-orifices with a small spatial interval and small angle. For examining the characteristics of the spray injected by the group-hole nozzle, the ultraviolet-visible laser absorption-scattering (LAS) imaging technique was adopted to determine vapor concentration and droplets density as well as other spray characteristics such as spray angle and penetration of both vapor and liquid phases.

In order to measure the droplets and vapor concentration inside a fuel spray, a dual-wavelength laser absorption-scattering technique was developed using the second harmonic (532nm) and the fourth harmonic (266nm) of a Nd:YAG laser and using dimethylnaphthalene as the test fuel. The investigation results show that dimethylnaphthalene, which has physical properties similar to diesel fuel, is almost transparent to visible light near 532nm and is a strong absorber of ultraviolet light near 266nm. Based on this result, the vapor concentration in a fuel spray can be determined by the two separate measurements: a transmission measurement at a non-absorbing wavelength to detect the droplets optical thickness and a transmission measurement at an absorbing wavelength to detect the joint vapor and droplets optical thickness. The droplets density can be determined by extinction imaging through the transmission at the non-absorbing wavelength.

Quantitative imaging of the fuel concentration distribution was made in the combustion chamber of a propane-fueled spark ignition (SI) engine with the employment of laser-sheet-induced Rayleigh scattering technique for realizing the remote, nonintrusive and highly space- and time-resolved measurement. The original engine was modified to introduce YAG laser-induced sheet light into the combustion chamber and the scattered light was captured by a CCD camera fitted with a gated double-micro- channel plate image intensifier. The measurements were done at the crank angle of 270°ATDC in the combustion chamber of the engine motored at 200rpm with an air fuel ratio of 13 for various injection timing, injection direction and intake flow. The results show that with an appropriate matching of fuel injection timing, injection direction and intake flow, a stratified distribution of the fuel concentration can be realized.

The fuel injection characteristics of Dimethyl Ether(DME) were calculated and compared with the calculated results of diesel fuel using a simulation model of an in-line diesel injection system in order to clarify the differences between the injection characteristics of the two fuels. Moreover, numerical analyses for the DME injection were performed while changing the fuel parameters and the injection system parameters in order to estimate the effects of these parameters on the fuel injection characteristics. The effects of some of these parameters were evaluated by experimental results conducted in a constant volume vessel. Furthermore, the spray tip penetration was calculated using the computed results of the injection pressure. As a result of this study, the injection characteristics of the DME fuel are basically confirmed. By the macroscopic analyses of these spray characteristics, the DME spray behavior in a combustion chamber can be estimated.

Spray combustion processes of palm oil biodiesel (PO) and conventional diesel fuels were simulated using the CONVERGE CFD code. Thermochemical and reaction kinetic data (115 species and 460 reactions) by Luo et al. (2012) and Lu et al. (2009) (68 species and 283 reactions) were implemented in the CONVERGE CFD to simulate the spray and combustion processes of the two fuels. Tetradecane (C14H30) and n- heptane (C7H16) were used as surrogates for diesel. For the palm biodiesel, the mixture of methyl decanoate (C11H20O2), methyl-9-decenoate (C11H19O2) and n-heptane was used as surrogate. The palm biodiesel surrogates were combined in proportions based on the previous GC-MS results for the five major biodiesel components namely methyl palmitate, methyl stearate, methyl oleate, methyl linoleate and methyl linolenate.

A comparison of spray characteristics was conducted between single- and multi-hole injectors. A commercial software (AVL FIRE) was used to investigate the internal flow inside the sac volume, as well as the initial spray behavior at 1 mm downstream of the nozzle exit. Microscopic imaging was applied to observe the spray dispersion angle (spray cone angle) at the vicinity of the nozzle. Laser absorption scattering (LAS) technique was implemented for measuring the mixture concentration. Three injection quantities, namely 0.5, 2.5, and 5.0 mg/hole, were selected to observe the differences between transient and quasi-steady spray. The vapor penetration at the initial stage of the injection was greater for single-hole than that of multi-hole injector due to faster fuel pressure build-up process inside the sac volume.

An early formation process of the spray, which was injected by a high-pressure swirl-type injector that is widely used in direct injection spark ignition (DISI) gasoline engines, was investigated through image analyzing techniques. The sprays were illuminated both by an Nd:YAG laser light sheet for getting the spray tomograms and by a tungsten lamp for getting the scattered back light shadow images of the sprays. The sprays were imaged by using a high-resolution CCD camera and a high-speed digital imaging system. The early development aspects of the spray were investigated in detail through the measurement of the tip penetration, cone angle and width of the early spray. At the start of injection, the liquid column emerges first, and it forms the “pre-swirl spray” without the swirl component. Following the liquid column, the liquid sheet emerges, however its radial velocity component is weak to form the complete hollow-cone spray. This spray changes into the “weak-swirl spray”.

Among the alternative fuels, dimethyl ether (DME), one of the oxygenated fuels, attracts attention as an alternative fuel for the Diesel engine since the properties of the DME are fitted to the Diesel engine combustion and the know-how development has been made of the mass production of the DME from a natural gas. In this study, experiments were performed of ignition characteristics of the DME and Diesel fuel sprays injected by a D.I. Diesel injector into a high-pressure, high-temperature vessel. The fuel injection was made by a Bosch type injection system. A schlieren optical system was adopted for visualizing the ignition process as well as the vaporization process of the DME and Diesel fuel sprays. The ignition delay was measured by using a photo-sensor which had a sensitivity in the wavelength range from visible to ultraviolet. Pressure and temperature of the ambient air and the oxygen concentration of the ambient air were changed as experimental parameters.

The group-hole (GH) nozzle concept that uses two closely spaced micro-orifices to substitute the conventional single orifice has the potential to facilitate better fuel atomization and evaporation, consequently attenuate the soot emission formed in direct-injection (D.I.) diesel engines. Studies of quantitative mixture properties of the transient fuel spray injected by the group-hole nozzles were conducted in a constant volume chamber via the laser absorption-scattering (LAS) technique, in comparison with conventional single-hole nozzles. Specific areas investigated involved: the non-evaporating and the evaporating ambient conditions, the free spray and the spray impinging on a flat wall conditions. The particular emphasis was on the effect of one of key parameters, the interval between orifices, of the group-hole (SH) nozzle structure.

A comprehensive model for sprays emerging from high-pressure swirl injectors in DISI engines has been developed accounting for both primary and secondary atomization. The model considers the transient behavior of the pre-spray and the steady-state behavior of the main spray. The pre-spray modeling is based on an empirical solid cone approach with varying cone angle. The main spray modeling is based on the Liquid Instability Sheet Atomization (LISA) approach, which is extended here to include the effects of swirl. Mie Scattering, LIF, PIV and Laser Droplet Size Analyzer techniques have been used to produce a set of experimental data for model validation. Both qualitative comparisons of the evolution of the spray structure, as well as quantitative comparisons of spray tip penetration and droplet sizes have been made. It is concluded that the model compares favorably with data under atmospheric conditions.

Ethanol is regarded as the promising alternative fuel for gasoline to meet the strict low emission standard for spark ignition engines. In this study, the spray mixture formation process for different ethanol blended fuels, including E0 (gasoline), E85 (85% volume of ethanol and 15% volume of gasoline) and E100 (ethanol), has been evaluated using hole-type nozzle by the measurement of Laser Absorption Scattering (LAS) technique in a constant volume vessel. Based on the principle of LAS, the quantitative vapor and liquid phase distribution from different ethanol blended fuel can be obtained by the light extinction regime. Aiming to analyze the effect of mixture formation and evaporation for different components of blended fuel or pure gasoline and ethanol, the vapor distribution of gasoline was determined by using p-xylene, which had similar physical properties to gasoline, especially higher boiling temperature components, and higher absorption for ultraviolet.

This paper studies the ignition processes of two biodiesel from two different feedstock sources, namely waste cooked oil (WCO) and palm oil (PO). They were investigated using the direct photography through high-speed video observations and detailed chemical kinetics. The detailed chemical kinetics modeling was carried out to complement data acquired using the high-speed video observations. For the high-speed video observations, an image intensifier combined with OH* filter connected to a high-speed video camera was used to obtain OH* chemiluminscence image near 313 nm. The OH* images were used to obtain the experimental ignition delay of the biodiesel fuels. For the high-speed video observations, experiments were done at an injection pressure of 100, 200 and 300 MPa using a 0.16 mm injector nozzle.

An investigation on the effect of dwell time of split injection on a diesel spray evolution and mixture formation process was carried out. A commercial 7-hole injector were used in the experiment to eliminate the possible discrepancies on the spray with single-hole research injector. Laser absorption scattering (LAS) technique was implemented for the measurement of the temporal evolution of fuel evaporation and mixture concentration. The diesel surrogate fuel consists of n-tridecane and 2.5% of 1-methylnaphthalene in volume basis was used. The total amount of fuel injected was initially fixed to 5.0 mg/hole. A split ratio of 9: 1 in mass basis was selected according to the results obtained from a previous study. The dwell time was varied from 120 µs to a negative value of −50 µs. The effects of negative dwell time was not ideal for lean mixture formation when compared to zero or positive dwell time conditions.

The effect of injection pressure ranging from 100 to 300MPa on the ignition, flame development and soot formation characteristics of biodiesel fuel spray using a common rail injection system for direct injection (D.I.) diesel engine was investigated. Experiments were carried out in a constant volume vessel under conditions similar to the real engine condition using a single hole nozzle. Biodiesel fuels from two sources namely; palm oil (BDFp) and cooked oil (BDFc) with the commercial JIS#2diesel fuel were utilized in this research. The OH chemiluminescence technique was used to determine the ignition and the lift-off length of the combusting flame. The natural luminosity technique was applied to study the flame development and the two color pyrometry was applied for the soot formation processes. Ignition delay decreased as the injection pressure progressed from 100 to 300MPa. This was as a result of the enhanced mixing achieved at higher injection pressures.

To reduce carbon dioxide emission and to relieve the demand of fossil fuels, ethanol is regarded as one of the most promising alternative fuels for gasoline. Recently, using ethanol in the state-of-the-art gasoline engine, direct-injection spark-ignition (DISI) engine, has become more attention by researchers due to less knowledge of the ignition and combustion processes in that engine. In this study, different ethanol-gasoline blended fuels, E0 (100% gasoline), E85 (85% ethanol and 15% gasoline mixed in volume basis) and E100 (100% ethanol) were injected by a valve-covered-orifice (VCO) hole-type nozzle. The experimental environment was set to the condition similar with the near top dead center (TDC) in DISI engine. The high-speed imaging of shadowgraph, OH* chemiluminescence and flame natural luminosity were used to clarify the characteristics of the ignition process, flame development and propagation.

Experimental results of a diesel engine have shown that using split-injection can reduce the NOx and particulate emissions. For understanding the mechanism of emissions reduction, mixture formation in split-injection diesel sprays was characterized in the present paper. A dual-wavelength laser absorption-scattering (LAS) technique was developed by use of the second harmonic (532nm) and the fourth harmonic (266nm) of a pulsed Nd:YAG laser as the incident light and dimethylnaphthalene (DMN) as the test fuel. By applying this technique, imaging was made of DMN sprays injected into a high-temperature and high-pressure constant volume vessel by a single-hole nozzle incorporated in a common rail injection system for D.I. diesel engine. The line-of-sight optical thickness of both fuel vapor and droplets in the sprays was yielded from the sprays images.

The objective of the paper is to characterize the diesel spray under the ambient conditions relevant for direct injection (D.I.) diesel engines. The particular emphasis is on the comparisons between laser measurements and predictions by empirical correlations and theoretical analyses. The ultraviolet-visible laser absorption-scattering (LAS) imaging technique is employed to quantitively determine the spray/mixture properties of the diesel spray injected by a hole-type injector, in terms of spray tip penetration and spatial concentration distributions of liquid and vapor phase. The structure of evaporating spray is obtained and analyzed. Based on the penetration correlations in the literature, a non-dimensional analysis of the spray tip penetration data is carried out. The results indicate that a self-similar state of the evaporating fuel spray is achieved.